Your school should give her an I-20 extending her F-2 when they extend your F-1 if you request this -- no need for new visa unless she leaves the U.S.

My mom's B2 visa I-94 expires on 12-20-2017. Applied Extension in Nov, 2017. How long can she stay in US legally? Any risks?

As long as her B-2 extension is pending she may stay. She may also leave before it is decided and advise to have it withdrawn.

What do I need to in order to obtain citizenship? Should I file N-600 or N-400?

You need a consult to determine this -- are you a permanent resident? If you were a PR before age 18 and Mom became a PR before you were 18 then...

What's the grace period for leaving the country after F1 reinstatement is denied? Is it 60 or 90 days?

There is no grace period following denial of F-1 reinstatement. You need to go home immediately. You can get a new I-20 and apply for a student...

I filed an I-360 VAWA and it was recently approved and I am undocumented in the U.S. can I apply for an I-765

You would have qualified for an EAD based on the prima facie determination which you probably received some time ago. You can file for EAD now or...

Recently I got my new L2 visa stamped till 2020. Do I need to get new EAD or just update new petition number?

Since you have an EAD valid until December 2020 no need to file for a renewal

What are the chances of an undocumented immigrant receiving an F1 visa to study in the U.S.

chances are reasonably good if you leave the U.S. ASAP with new I-20 and apply for a student visa.

What can I do in situation when I came in US on h4 dependent visa and I think husband didn’t extended my h4 visa.

If you did not file to extend before your current status expired you may be out of luck unless you go home with your husband's new H-1B approval...

How do I go about marrying an illegal immigrant and getting him his visa

The steps depend on whether you are a permanent resident or U.S citizen and whether he was ever in a legal status in the U.S. If he entered...

What to do when My EAD is expired in with pending I-485?

Unfortunately there is not much to do as the EAD's are taking 6-8 months in this category and won't be expedited except under extreme facts.